There are several kinds of traditional camera lens, including normal lens, telephoto lens, wide-angle lens and so on. Among the several camera lenses, the wide-angle lens is a lens by which the range of a camera can be shot in a wider viewing angle, and according to the wide-view characteristic of the wide-angle lens, it is generally widely applied in a camera device for a monitor or car. At present, the miniaturization of camera devices becomes a trend of social development, and demands are increasing for small wide-angle lens with a viewing angle exceeding 180°.
A wide-angle lens mounted in a camera device has a relatively short optical length. The optical length is a distance from an incident plane to an imaging plane (i.e., an illuminated face of an image sensor) of an object plane of the wide-angle lens. In addition, in order to achieve the microminiaturization of the wide-angle lens, the ratio of the focal distance of the wide-angle lens to the above optical length should be also reduced.
Since an existing wide-angle lens is made up of a plurality of lens elements, therefore at present, the number of the lens elements inside the wide-angle lens is required to as few as possible to form a small wide-angle lens. However, the fewer lens elements in the wide-angle lens, the lower ability the optical aberration compensation has, and ultimately leads to worse image quality formed in the imaging plane.
In addition, the wide-angle lens is generally used in different circumstances. If the wide-angle lens is mounted outside the car, the surface of a first lens element located on the object plane can be exposed to a variety of severe conditions such as UV (ultraviolet ray), acid rain, dust, rubble and so on. Normal resin lens is harder to bear such circumstances.